Viral loads of parainfluenza virus type 3 and severity of respiratory diseases in children.

BACKGROUND: Parainfluenza virus type 3 (PIV-3) is one of the common pathogens for respiratory infections in children. Whether viral load of PIV-3 is associated with severity of respiratory diseases in children is not yet known. Our aim was to determine significance of PIV-3 viral load among infected children. METHODS: We conducted a single-center, retrospective study at Tokyo Metropolitan. Children's Medical Center, Japan, from June to August 2021. Hospitalized children were screened with a posterior nasal swab for multiplex PCR, and viral load was subsequently measured from remained samples by real-time PCR. Demographic data were collected from digital charts. PIV-3 positive patients were categorized into mild group with no oxygen demand, moderate group with low-flow oxygen demand and severe group with high-flow nasal cannula oxygen or non-invasive positive pressure ventilation or mechanical ventilation. Viral loads were compared among mild, moderate and severe groups. RESULTS: 151 patients were positive for PIV-3. We found no statistically significant association among PIV-3 viral load and severity of respiratory diseases (p = 0.35), and no statistically significant association between severity of illness and co-detection of other viruses. In each severity group, relatively high viral load per posterior nasal swab was observed at the time of testing. CONCLUSION: Among PIV-3 patients, we could not find statistically significant between viral load and their severity, therefore we could not conclude that viral load is a good surrogate marker for clinical severity of PIV-3.

Clinical characteristics and treatment of IMP-type carbapenemase-producing Enterobacteriaceae bacteremia: Case series and literature review.

BACKGROUND: Several carbapenemases have been identified globally in Enterobacteriaceae. In Japan, IMP-type carbapenemase is the most prevalent, although cases of carbapenemase-producing Enterobacteriaceae (CPE) bacteremia are still scarce. The present case series and literature review aimed to elucidate the clinical characteristics and treatment strategies for IMP-type CPE bacteremia. METHODS: Clinical data on pediatric cases of IMP-type CPE bacteremia at the Tokyo Metropolitan Children's Medical Center between 2010 and 2020 were collected, and a review of past studies of IMP-type CPE bacteremia has been provided. RESULTS: Five pediatric episodes of IMP-type CPE bacteremia were identified. Our review of previous literature on IMP-type CPE bacteremia revealed 24 adult patients, but no pediatric patients. All 29 cases had underlying diseases, and 23 (79%) received combination therapy. The median duration of antibiotic therapy was 14 days (interquartile range: 9-14 days). The overall mortality rate was 38% (11/29). The mortality rates associated with monotherapy and combination therapy were 67% (4/6) and 30% (7/23), respectively. CONCLUSIONS: We report the first case series of IMP-type CPE bacteremia in children. Our review of past studies suggests that combination therapy might lead to better survival outcomes in patients with IMP-type CPE bacteremia. Further research is needed to establish an optimal treatment strategy for IMP-type CPE bacteremia.

CTX-M group gene distribution of extended spectrum beta-lactamase-producing Enterobacteriaceae at a Japanese Children's hospital.

Extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae have spread globally as one of the most common multidrug resistant organisms. Although a wide variety of ESBL genes were known in each geographical region, few reports existed on the distribution of ESBL genes in Japanese children. To clarify the distribution of ESBL genes, we investigated the CTX-M type of the ESBL-producing Enterobacteriaceae and patient characteristics among hospital-acquired and community-acquired cases. Total of 253 isolates of ESBL-producing Enterobacteriaceae were recovered from 238 pediatric patients. ESBL-producing Enterobacteriaceae were mostly recovered from children with underlying diseases (76.5%). Ratio of community-acquired and hospital-acquired cases was 58.8% and 41.2%, respectively. Compared to the hospital-acquired cases, community-acquired cases had younger age, fewer underlying diseases, and the dominant detection of Escherichia coli. The most common ESBL-producing Enterobacteriaceae was E. coli (79.8%), followed by Klebsiella pneumoniae (9.1%). CTX-M9 group was the most prevalent CTX-M group gene (63.2%), which was dominantly detected in E. coli (72.7%). This was the largest descriptive study to find CTX-M9 group as the most prevalent ESBL genotype among Enterobacteriaceae isolated from Japanese children in line with adult's epidemiology.

First report on USA300 outbreak in a neonatal intensive care unit detected by polymerase chain reaction-based open reading frame typing in Japan.

Outbreaks of methicillin-resistant Staphylococcus aureus (MRSA) in the neonatal intensive care unit (NICU) have been reported worldwide. Some outbreaks were caused by USA300, which is a community-associated MRSA clone. In 2011, polymerase chain reaction-based open reading frame typing (POT) for the initial MRSA isolates from all inpatients was started at the Tokyo Metropolitan Children's Medical Center. From March 2014 to April 2015, a total of 131 MRSA strains were isolated, 104 of which were analyzed as healthcare-associated MRSA. Thirteen stains (12.5%) had a POT number of 106-9-93, which strongly suggested USA300; these included 6 from nasal swabs, 6 from blood cultures and 1 from subcutaneous pus. All the MRSA strains were isolated from patients in the NICU; were typed as sequence type 8, spa type t008, and staphylococcal cassette chromosome type mec IVa; and possessed the lukS-lukF and arginine catabolic mobile element-arcA gene. Pulsed-field gel electrophoresis of all the strains, with USA300-0114 as a reference, showed indistinguishable banding pattern. Based on these results, POT was useful in recognizing this first MRSA outbreak of USA300 in a Japanese NICU and was advantageous in terms of swiftness, less cost and monitoring change of the epidemic MRSA lineage.

Enterovirus D68 respiratory infection in a children's hospital in Japan in 2015.

BACKGROUND: Outbreaks of enterovirus D68 (EV-D68) respiratory infections in children were reported globally in 2014. In Japan, there was an EV-D68 outbreak in the autumn of 2015 (September-October). The aim of this study was to compare EV-D68-specific polymerase chain reaction (PCR)-positive and EV-D68-specific PCR-negative patients. METHODS: Pediatric patients admitted for any respiratory symptoms between September and October 2015 were enrolled. Nasopharyngeal swabs were tested for multiplex respiratory virus PCR and EV-D68-specific reverse transcription-PCR. EV-D68-specific PCR-positive and -negative patients were compared regarding demographic data and clinical information. RESULTS: A nasopharyngeal swab was obtained from 76 of 165 patients admitted with respiratory symptoms during the study period. EV-D68 was detected in 40 samples (52.6%). Median age in the EV-D68-specific PCR-positive and -negative groups was 3.0 years (IQR, 5.5 years) and 3.0 years (IQR, 4.0 years), respectively. The rates of coinfection in the two groups were 32.5% and 47.2%, respectively. There was no significant difference in the history of asthma or recurrent wheezing, length of hospitalization, or pediatric intensive care unit admission rate between the groups. The median days between symptom onset and admission was significantly lower for the EV-D68-positive group (3.0 days vs 5.0 days, P = 0.001). EV-D68 was identified as clade B on phylogenetic analysis. No cases of acute flaccid myelitis were encountered. CONCLUSIONS: More than half of the samples from the children admitted with respiratory symptoms were positive for EV-D68-specific PCR during the outbreak. Asthma history was not associated with the risk of developing severe respiratory infection.

Sibling visits and viral infection in the neonatal intensive care unit.

BACKGROUND: Sibling visits to the neonatal intensive care unit (NICU) are a part of family-centered care, which is now being increasingly endorsed as a positive development in patient care. Sibling visits, however, pose a risk of viral infection, and hence many NICU in Japan impose strict limits on the practice. The aim of this study was therefore to assess whether sibling visits to the NICU are related to an increase in the nosocomial viral infection rate. METHODS: This retrospective study was conducted between April 2012 and March 2017 at Tokyo Metropolitan Children's Medical Center in Japan. Sibling visits were implemented after screening for symptoms of viral illness. Symptomatic patients in the NICU were tested for common viruses on rapid antigen test and polymerase chain reaction. The number of sibling visits and the rate of nosocomial viral infections were examined on Spearman's correlation test. RESULTS: The total number of sibling visits and rate of nosocomial viral infection in the NICU was 102 and 0.068 per 1,000 patient-days during the study period, respectively. The number of enterovirus, respiratory syncytial virus, human metapneumovirus, influenza virus A, and Herpes simplex virus infections was 3, 2, 1, 1, 1, and 1, respectively. No infections were identified after sibling visits. The number of sibling visits and the rate of nosocomial viral infections were not correlated (correlation coefficient, -0.1; P = 0.873). CONCLUSION: Sibling visits to the NICU did not result in an increase in the nosocomial viral infection rate.

Comparison of USA300 with non-USA300 methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit.

OBJECTIVES: Reports of USA300 methicillin-resistant Staphylococcus aureus (MRSA) strain were still scarce in neonatal intensive care units (NICUs) and the relationship of USA300 MRSA to clinical infections is still controversial. The primary outcome was the incidence of MRSA infections caused by the USA300 and non-USA300 strains at a NICU in Japan. METHODS: This retrospective cohort study was conducted between November 2011 and October 2016 at Tokyo Metropolitan Children's Medical Center in Japan. All MRSA isolated after 48h of hospitalization were included for analysis by pulsed-field gel electrophoresis (PFGE) using the standard USA300 strain. Genes were tested for Panton-Valentine leukocidin (PVL) and arginine catabolic mobile element (ACME). A whole genome sequence was performed for representative isolates of USA300. RESULTS: In total, 109 MRSA isolates were included for analysis. PFGE classified 34 and 75 isolates of USA300 and non-USA300 MRSA, respectively. Both PVL and ACME genes were detected in USA300 and non-USA300 strains at rate of 100% (34/34) and 5.3% (4/75), respectively (P<0.05). There was no statistically significant difference in the proportion of clinical diseases between USA- 300 and non-USA 300 strains. CONCLUSIONS: Infants with USA300 MRSA infection did not differ significantly from those with non-USA300 MRSA infection.

Scalable purification of adeno-associated virus serotype 1 (AAV1) and AAV8 vectors, using dual ion-exchange adsorptive membranes.

In vivo gene transduction with adeno-associated virus (AAV)-based vectors depends on laborious procedures for the production of high-titer vector stocks. Purification steps for efficient clearance of impurities such as host cell proteins and empty vector particles are required to meet end-product specifications. Therefore, the development of alternative, realistic methods to facilitate a scalable virus recovery procedure is critical to promote in vivo investigations. However, the conventional purification procedure with resin-based packed-bed chromatography suffers from a number of limitations, including variations in pressure, slow pore diffusion, and large bed volumes. Here we have employed disposable high-performance anion- and cation-exchange membrane adsorbers to effectively purify recombinant viruses. As a result of isoelectric focusing analysis, the isoelectric point of empty particles was found to be significantly higher than that of packaged virions. Therefore, AAV vector purification with the membrane adsorbers was successful and allowed higher levels of gene transfer in vivo without remarkable signs of toxicity or inflammation. Electron microscopy of the AAV vector stocks obtained revealed highly purified virions with as few as 0.8% empty particles. Furthermore, the membrane adsorbers enabled recovery of AAV vectors in the transduced culture supernatant. Also, the ion-exchange enrichment of retroviral vectors bearing the amphotropic envelope was successful. This rapid and scalable viral purification protocol using disposable membrane adsorbers is particularly promising for in vivo experimentation and clinical investigations.